
1. Open your start image, I'm using a street scene because it has natural lines of perspective that are easy to see.
2. Make a new layer above this one. This will be for the perspective lines.
3. Go to the Shapes Tool on the toolbar -

On the menu bar at the top, select 3px for the weight and red for the colour.
4. Now, working on the empty layer, draw your first perspective line following the natural line at the top of the shop fronts. Press Enter. Draw the second perspective line following the natural line at the bottom of the shop fronts. Press Enter. Where the two lines cross is the vanishing point. Still using the Line Tool change the colour to green and draw a line from the vanishing point back across the image to represent the eye level. Press Enter. You should have something like this -
5. Place your subject over on the left of the image. Make sure that the subject's eyes are level with the green line.

6. Now comes the clever bit. Make a copy of the subject layer (Layer>Duplicate Layer) and press Ctrl+T to
bring up the Transform Tool. Click and hold on the center mark -
and re-position it on the vanishing point.
7. Now, while holding down Shift+Alt, drag the top left corner handle towards the vanishing point. You should see your subject move to the right and decrease in size whilst maintaining perspective.

8. Not happy with just two subjects? Hold down Shift+Ctrl+Alt and press 'T' a few times. Amazing or what?
9. All that remains is to delete the perspective lines and flatten the image. Obviously this is just a quick demo and you would put a bit of shadow underneath the original subject so that it gets repeated with each addition.